Comprehensive Characterisation of n-Alkylresorcinols and Other Lipid Constituents of Mercurialis tomentosa L. from Alicante, Spain.

Mercurialis tomentosa L. has been used in Spanish ethnomedicine. In the present study the first phytochemical characterisation of a lipid fraction from M. tomentosa was performed. The CHCl3 extraction of aerial parts from M. tomentosa and GC/MS investigations revealed the occurrence of cuticular lipid and wax constituents, like long chain n-alcohols and n-aldehydes (C22  - C30 ), besides several aromatic constituents, i.e., phenylpropanoids and n-alkylresorcinols. The latter were further purified by CC and analysed by LC/MSn . In contrast to other Mercurialis species, i.e., M. annua, M. perennis, which exclusively contain 5-n-alkylresorcinols (1a - j, Cn ), mainly 5-n-alkyl-2-methylresorcinols (2a - j, Cn *) with side chain lengths of C15  - C25 were found in M. tomentosa, in addition to 1a - j. Thus, the latter compounds may be utilised for analytical characterisation and authentication of M. tomentosa based on fingerprinting methods. For structure elucidation a novel facile total synthesis of one representative 5-n-alkyl-2-methylresorcinol homologue (2d, C19 *) was developed, starting with a Grignard reaction from a substituted benzoic acid chloride (19). The compound obtained by synthesis was identical to the natural product 2d in terms of its chromatographic and spectroscopic features. Futhermore, 2d exhibited satisfactory DPPH free radical scavenging activity (IC50  = 37.8 μm) when compared to trolox (IC50  = 21.0 μm), corroborating the antioxidant features of these amphipathic molecules.